Systems and methods for probing wired communication channels

ABSTRACT

Various systems and methods for probing a communication channel. These systems and methods transmit an error vector probe packet from a first transmitter while a second transmitter is active and transmitting. A network device may receive the error vector probe packet and measure an error vector magnitude based on the received error vector probe packet. Using the error vector magnitude, the network device estimates channel characteristics such as signal-to-noise ratio, data capacity, etc. The transmission can occur when more than one transmitter is active and transmitting. At least some of the other transmitters are active and transmit an analog zero signal, e.g., all digital zeros on the input to the digital-to-analog converter of a network device when an error vector probe packet is transmitted.

TECHNICAL FIELD

This disclosure relates to communication systems, and at least some ofthe examples disclosed herein relate more specifically to systems andmethods for probing a wired communication channel.

DESCRIPTION OF THE RELATED ART

FIG. 1 is a diagram that illustrates an example of a wirelessenvironment. An area 100 includes various transmitting and receivingdevices 102, 104 and 106. These devices 102, 104 and 106 can includemobile phones, radio and television transmitters, wireless networkingdevices, etc. Some of the devices 102, 104 and 106 are mobile devices;some are not mobile. Mobile or not, however, the communicationenvironment in which these devices operate is constantly changing.Signals from these devices 102, 104 and 106 reflect off buildings 108,vehicles 110 and 112, hills 114 and other features of the geographicarea 100. Further, features of the area 100 are changing. Vehicles 110and 112 move, people move within the area 100, weather patterns change,new buildings are built, etc. All of these and many other factors leadto a constantly changing communications environment.

The characteristics of wired communications channels, on the other hand,tend to be more consistent, even though they may vary with temperature,equipment changes, etc. Because of this relative consistency, it can beadvantageous to estimate certain channel characteristics in ways notused in a wireless communication system, even if these wired systems usesimilar modulation techniques.

One example of a wired system is the system defined by the Multimediaover Coax Alliance (MoCA™). In a MoCA system, coaxial cables are used toconnect components of the network, such as antennas, TVs, set top boxesand radios, and generally to distribute cable TV signals throughout ahome or building. MoCA systems are generally used to allow suchentertainment devices within a home network to communicate with oneanother and share data, including multimedia data, such as televisionshows, movies, internet data, music, video clips, etc. One advantage ofsuch MoCA systems is that new home wiring might be avoided because manyhomes already have adequate coaxial wiring installed. MoCA systems aretypically used to distribute high-quality multimedia content andhigh-speed data with throughput exceeding 100 megabit per second.

MoCA devices generally communication with one another in the 1 GHzmicrowave band using orthogonal frequency-division multiplexing (OFDM)modulation. The OFDM modulated signals used by MoCA are communicatedover MoCA channels using a frequency-division multiplexing (FDM). InMoCA systems that use OFDM, each MoCA channel is formed from one of alarge number of closely spaced orthogonal sub-carriers. These MoCAchannels are typically used to carry data. Each sub-carrier is typicallymodulated with a conventional modulation scheme at a low symbol rate,maintaining total data rates similar to conventional single-carriermodulation schemes in the same bandwidth. Some example modulationsinclude quadrature amplitude modulation (QAM) or phase shift keying(PSK) modulation.

In order to take advantage of the maximum bandwidth of each channel, itis necessary to characterize the channel between each device and eachother device. The characteristics of each channel are determined bytransmitting an error vector magnitude (EVM) probe from one device thatrepresents a node in the network to each other device that represents anode on the network. Each such receiving device measures the value ofthe EVM probe. The measurements are then used to determine thecharacteristics of the channel between the transmitting device and thereceiving device. However, the characteristics of the channel willchange depending upon which of the other devices on the network aretransmitting at any particular time.

In current MoCA systems, the only device that is transmitting when achannel is being measured is that device that is sending the EVM probesused to measure the characteristics of the channels between thetransmitting device and the other devices of the network. But, inOrthogonal Frequency Division Multiple Access (OFDMA) mode, when contentis being communicated between the devices of the network, the networkwill support several devices transmitting at the same time, each ondifferent channels using a different sub-carrier for each channel.

Accordingly, the characteristics measured for each channel will onlyaccurately reflect the actual characteristics of the channel if there isonly one device transmitting at a time. This mischaracterization of thechannels can lead to inefficiency in the use of the bandwidth of thenetwork. Therefore, there is a need for a method and apparatus formeasuring the characteristics of each channel without having to transmitEVM probes under each possible situation in which there is a uniquecombination of devices transmitting concurrently on other channels.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

Various embodiments of systems and methods for probing a wiredcommunication channel are presented. Various embodiments of thedisclosed method and apparatus are directed toward systems and methodsfor characterizing a wired communication channel. In variousembodiments, these systems and methods transmit an error vectormagnitude (EVM) probe packet from a first transmitter while a secondtransmitter is active and transmitting. A network device, such as anetwork controller can receive the EVM probe packet and measure an EVMbased on the received EVM probe packet. Using the EVM, the networkcontroller or other network device may estimate channel characteristicssuch as signal-to-noise ratio, data capacity, etc.

In various embodiments, the transmission of an EVM probe packet occurswhen more than one transmitter is active and transmitting. In such acase, the additional transmitters are transmitting an analog zerosignal, i.e., all digital zeros on the input to the digital-to-analogconverter that drives the transmission circuitry in the network device.For a device on a wired network to present the same or similar impedanceto the rest of the network as that device presents when the network iscarrying user data, the device should be transmitting when an EVM probepacket is transmitted from another network device.

In various embodiments, the estimation of channel characteristics occursat a network device. For example, the estimation may occur at a networkcontroller. In such an example, one network device transmits a probepacket while other network devices are transmitting a known datasequence. A network controller receives the probe packet and the networkcontroller then determines various channel characteristics, e.g.,signal-to-noise ratio, channel capacity, etc.

In various embodiments, the channel characteristic that is estimated isbased on the magnitude of the error vector as determined upon receipt ofthe EVM probe packet. Some example channel characteristics that can beestimated include signal-to-noise ratio, data capacity, etc.Additionally, various methods and systems calculate a power settingbased on a previous determination of the magnitude of an error vector,wherein the EVM probe packet is transmitted while a second transmitteris active and transmitting an analog zero signal.

Various embodiments transmit a second EVM probe packet from a secondtransmitter while a first transmitter is active and transmitting on awired communication channel, such as a MoCA network. In suchembodiments, the EVM probe packet is received and variouscharacteristics are determined. In some of these embodiments, themagnitude of a second error vector for the second transmitter is alsomeasured based on the received second EVM probe packet. The channelcharacteristics for the second transmitter are estimated based on themagnitude of the second error vector. The second transmitter operates ina configuration used to transmit data packets. In one example in whichthe channel characteristics for the second transmitter are notestimated, an analog zero signal is transmitted by the secondtransmitter.

Other features and aspects of the disclosed method and apparatus willbecome apparent from the following detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the features in accordance with embodiments. The summary is notintended to limit the scope of the invention, which is defined solely bythe claims attached hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed method and apparatus, in accordance with one or morevarious embodiments, is described in detail with reference to thefollowing figures. The drawings are provided for purposes ofillustration only and merely depict typical or example embodiments ofthe claimed invention. These drawings are provided to facilitate thereader's understanding of the disclosed method and apparatus and shouldnot be considered limiting of the breadth or scope of the claimedinvention. It should be noted that for clarity and ease of illustrationthese drawings are not necessarily made to scale.

FIG. 1 is a diagram that illustrates an example wireless environment.

FIG. 2 is a diagram that illustrates an example entertainment network inaccordance with the systems and methods described herein.

FIG. 3 is a block diagram that illustrates an example wiredcommunication network in accordance with the systems and methodsdescribed herein.

FIG. 4 is another block diagram that illustrates an example wiredcommunication network in accordance with the systems and methodsdescribed herein.

FIG. 5 is a flow chart illustrating an example method in accordance withthe systems and methods described herein.

FIG. 6 is a block diagram illustrating an example network device inaccordance with the systems and methods described herein.

The figures are not intended to be exhaustive or to limit the disclosedmethod and apparatus to the precise form disclosed. It should beunderstood that the disclosed method and apparatus can be practiced withmodification and alteration. The claimed invention should be definedonly by the claims and the equivalents thereof.

DETAILED DESCRIPTION

The disclosed method and apparatus relates to communication systems, andmore particularly, various embodiments relate to systems and methods forprobing a wired communication channel. While MoCA using OFDM ispresented as an example system below, it will be understood by those ofskill in the art that other wired communication systems may also use thedisclosed method and apparatus. Various embodiments of the disclosedmethod and apparatus are directed toward characterizing a wiredcommunication channel using an error vector magnitude (EVM) probe packetto measure the magnitude of an error vector (i.e., the EVM). Inaccordance with various embodiments of the disclosed method andapparatus, the EVM is used to determine various characteristics of thenetwork, such as signal-to-noise ratio, data capacity, etc.

In various embodiments, these systems and methods transmit an EVM probepacket from a first transmitter while a second transmitter istransmitting. The impedance of the second transmitter during the timewhen the channel is being characterized will be the same or similar toits impedance when operating in the network.

In various embodiments, a network device, such as a network controller,receives an EVM probe packet and measures the EVM based on the receivedEVM probe packet. The network controller or other network deviceestimates channel characteristics using the EVM.

FIG. 2 is a diagram that illustrates an example entertainment network202 in accordance with the systems and methods described herein. Theentertainment network 202 is located in a typical family home 200.However, it will be understood that the systems and methods describedherein can be applied to various other types of buildings or outdoorlocations that might use communication networks, such as, but notlimited to, the entertainment network 202 illustrated in FIG. 2.

The home 200 is provided with entertainment services through aconnection 204 with an entertainment service provider. This connectionmay be a wired or wireless connection such as cable, satellite, fiberoptic, or other communication connection and can include internetservice, television programming, etc.

In various embodiments, connection 204 supports the communication ofcontent associated with multiple data services from multiple serviceproviders. For example, a homeowner might use satellite receivers forreceiving television content and Digital Subscribers Line (DSL) serviceto receive internet service. These services might all be connected to anetwork device 206 that then provides these services to people in thehome 200 over a wired home network 208. The wired network might usetypical computer network wiring or other types of wiring. For example,the home network 208 might use Ethernet cabling or coaxial cable with anetwork defined by a communication standard, such as MoCA 1.0. A MoCA orsimilar network is easy to set up in homes 200 in which adequate coaxialcables have been previously installed.

In various examples, telephone services are provided using connection204. These services are then routed throughout the home 200 over thewired network 208. Alternatively, these telephone services are connectedfrom the network device 206 to a separate telephone system (not shown)within the home 200. As will be understood by those skilled in the art,many different combinations of services provided using connection 204and methods of distribution within the home 200 are possible and varyfrom embodiment to embodiment.

In one embodiment, the network device 206 is a network controller. Insuch an embodiment, the controller 206 provides control functionalityfor the network 208. This network 208 is a MoCA network in variousembodiments. In the example network 208, internet services andtelevision services are provided through the network 208. As illustratedin FIG. 2, the network 208 is connected to network devices 210, 212 and216. Network devices 210 and 212 are set top boxes that providetelevision programming content that can be viewed using the televisions218 and 220. Network device 216 provides a computer network connection226 to a personal computer 228. For example, personal computer 228 isconnected to the internet using network device 216.

Channel characteristics can be determined for the network 208 bytransmitting an EVM probe packet while a second transmitter istransmitting. The EVM is determined for the EVM probe packet. In variousembodiments, the network device 216 can also include a wirelesscomponent, such as 802.11.80 to which other computers can connect toe.g., over the internet.

FIG. 3 is a block diagram that illustrates an example wiredcommunication network in accordance with the systems and methodsdescribed herein. In FIG. 3, a communications network, such asentertainment network 300, includes network devices 302, 304, and 306.One or more network devices 306 can be a network controller 306. Thenetwork controller controls various aspects of the network 300.

The network devices 302, 304, and 306 are connected together over awired connection 308. The channel characteristics of the wiredconnection 308 generally tend to be consistent, but may change over timedue to temperature changes, wiring changes, equipment changes and otherfactors.

FIG. 4 is a block diagram that illustrates an example wiredcommunications network in accordance with the systems and methodsdescribed herein. In FIG. 4, the entertainment network 400 includes anadditional network device 402. FIG. 4 illustrates that the entertainmentnetwork 300 of FIG. 3 may be modified with one or more additionalnetwork devices 402. Because these changes may be infrequent, thenetwork characteristics are relatively consistent over time.Accordingly, communication channel probing is preformed infrequently invarious embodiments.

As illustrated in FIGS. 3 and 4 the entertainment networks 300 and 400are wired networks. Because of this, each of the devices 302, 304, 306and 402 affects other devices in networks 300 and 400. When estimatingchannel characteristics these effects should be accounted for by placingeach network device 302, 304, 306 and 402 in the same mode orconfiguration it will be in when the network is transmitting datapackets (e.g., providing users with entertainment content). In variousembodiments, this is done by transmitting communication probes from onedevice 302, 304, 306, or 402 while one or more additional devices 302,304, 306, or 402 are transmitting.

FIG. 5 is a flow chart illustrating an example method in accordance withthe systems and methods described herein. In step 500, a devicetransmits a first EVM probe packet. For example, device 302 transmitsthe first EVM probe packet. While device 302 is transmitting the packet,the other devices 304, 306, and 402 are also transmitting. In oneembodiment, devices 304, 306, and 402 transmit an “analog zero” signal.The analog zero signal is created by transmitting when a logical zero isinput to a digital-to-analog converter that drives a transmitter in thedevices 304, 306, and 402.

In step 502, a device receives the vector probe packet. In variousembodiments, a network controller, another network device, or a receiverwithin the transmitting device receives the vector probe packet. In onesuch embodiment, the processing of steps 504 and 506 occurs in one ormore network devices, in a network controller, or in the device thattransmitted an EVM probe packet.

In step 504, a device measures the EVM for a transmitter based on thereceived EVM probe packet. The EVM for the transmitter may be the sameor similar to the EVM of the network when it is functioning to provideentertainment content to various areas of, e.g., the home, because allor some of the other devices in the network have the same or similarimpedance. It should be noted that the impedance of a device can changedepending upon whether the device is transmitting and the particularpower level of the transmission.

In step 506, a device estimates channel characteristics based on theEVM. The channel characteristics that are estimated based on the EVM cancomprise data capacity or signal-to-noise ratio. In various embodiments,steps 502, 504 and 506 occur in a network controller, network device orthe transmitting device.

It will be understood by those skilled in the art that the methodsdisclosed herein easily lend themselves to being programmed intocomputer readable code which is then stored on a tangible computerreadable storage medium, such as a magnetic disk or integrated circuit.

In various embodiments, the method includes determining a power settingbased on a previous OFDM or OFDMA EVM determination. It should beunderstood by those skilled in the art that there are several ways thepower setting can be determined. For example, a power setting can bebased on power measurements of previously received packets that may ormay not include an EVM probe packet. The receiver communicates to thetransmitter the level to use. Alternatively, an assumption is made thatthe channel is reciprocal (i.e., that the characteristics of the channelare the same in each direction) and the transmitter then uses powermeasurements made on the channel the transmitter is receiving.

FIG. 6 is a diagram illustrating a simplified block diagram of anexample network device in accordance with the systems and methodsdescribed herein. In FIG. 6 the example network device 600 includesreceiver circuitry 602 and transmitter circuitry 604. The receiver andtransmitter circuitry 602 and 604 are coupled to a processor 606. Invarious embodiments, the processor 606 is a microprocessor,microcontroller, describe logic, programmable logic, ASIC, FPGA, etc. Inother embodiments, the processor 606 is a combination of these. Theprocessor 606 is coupled to a memory 608. In one embodiment, the memory608 stores instructions, data, or both. For example, instructionsimplementing the methods described herein can be stored in the memory608, such as a tangible computer readable storage medium.

As illustrated in FIG. 6, the receiving circuitry 602 and thetransmitter circuitry 604 are connected to wired network 610 through areceiver/transmitter filter 612. It will be understood by those of skillin the art that other network devices that may be used to implement thesystems and methods described herein may have a separate receivercircuitry 602 input and a separate transmitter circuitry 608 output.

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not of limitation. Likewise, the various diagrams maydepict an example architectural or other configuration for theinvention, which is done to aid in understanding the features andfunctionality that can be included in the invention. The invention isnot restricted to the illustrated example architectures orconfigurations, but the desired features can be implemented using avariety of alternative architectures and configurations. Indeed, it willbe apparent to one of skill in the art how alternative functional,logical or physical partitioning and configurations can be implementedto implement the desired features of the present invention. Furthermore,a multitude of different constituent module names other than thosedepicted herein can be applied to the various partitions. Additionally,with regard to flow diagrams, operational descriptions and methodclaims, the order in which the steps are presented herein shall notmandate that various embodiments be implemented to perform the recitedfunctionality in the same order unless the context dictates otherwise.

Although the invention is described above in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the otherembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as meaning “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; the terms “a” or“an” should be read as meaning “at least one,” “one or more” or thelike; and adjectives such as “conventional,” “traditional,” “normal,”“standard,” “known” and terms of similar meaning should not be construedas limiting the item described to a given time period or to an itemavailable as of a given time, but instead should be read to encompassconventional, traditional, normal, or standard technologies that may beavailable or known now or at any time in the future. Likewise, wherethis document refers to technologies that would be apparent or known toone of ordinary skill in the art, such technologies encompass thoseapparent or known to the skilled artisan now or at any time in thefuture.

The presence of broadening words and phrases such as “one or more,” “atleast,” “but not limited to” or other like phrases in some instancesshall not be read to mean that the narrower case is intended or requiredin instances where such broadening phrases may be absent. The use of theterm “module” does not imply that the components or functionalitydescribed or claimed as part of the module are all configured in acommon package. Indeed, any or all of the various components of amodule, whether control logic or other components, can be combined in asingle package or separately maintained and can further be distributedin multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described interms of exemplary block diagrams, flow charts and other illustrations.As will become apparent to one of ordinary skill in the art afterreading this document, the illustrated embodiments and their variousalternatives can be implemented without confinement to the illustratedexamples. For example, block diagrams and their accompanying descriptionshould not be construed as mandating a particular architecture orconfiguration.

1. A method of probing a wired communication channel comprising: a)receiving a first error vector probe packet that was transmitted by afirst transmitter while a second transmitter in a system is transmittingon the wired communication channel; b) measuring an error vectormagnitude for the first transmitter based on the received first errorvector probe packet; and c) estimating channel characteristics based onthe error vector magnitude.
 2. The method of claim 1, further comprisingtransmitting the first error vector probe packet from the firsttransmitter, while the second transmitter in a system is transmitting onthe wired communication channel.
 3. The method of claim 1, wherein thechannel characteristic that is estimated based on the error vectormagnitude comprises a signal-to-noise ratio.
 4. The method of claim 1,wherein the channel characteristic that is estimated based on the errorvector magnitude comprises a data capacity.
 5. The method of claim 1,wherein the first transmitter transmits a probe packet, while more thanone additional transmitter is active and transmitting.
 6. The method ofclaim 1, further comprising: a) receiving the second error vector probepacket that has been transmitted from a second transmitter, while thefirst transmitter is active and transmitting on the wired communicationchannel; b) measuring a second error vector magnitude for the secondtransmitter based on the received second error vector probe packet; andc) estimating channel characteristics for the second transmitter basedon the second error vector magnitude.
 7. The method of claim 1, furthercomprising determining a power setting based on a previous error vectormagnitude determination.
 8. The method of claim 1, wherein the probepacket is transmitted while a second transmitter is active andtransmitting an analog zero signal.
 9. The method of claim 1, whereinthe estimation occurs at a network controller.
 10. The method of claim1, wherein the second transmitter operates in a configuration used totransmit data packets.
 11. A wired communication system comprising: a) afirst transmitter configured to transmit a first error vector probepacket on a wired communication channel while a second transmitter inthe system is active and transmitting on the wired communicationchannel; b) a receiver configured to receive the first error vectorprobe packet; and c) a processor configured to measure an error vectormagnitude for the first transmitter based on the received error vectorprobe packet and to estimate a channel characteristic based on the errorvector magnitude.
 12. The system of claim 11, wherein the channelcharacteristic that the processor estimates based on the error vectormagnitude comprises a signal-to-noise ratio.
 13. The system of claim 11,wherein the channel characteristic that the processor estimates based onthe error vector magnitude comprises a data capacity.
 14. The system ofclaim 11, wherein the first transmitter transmits a probe packet, whilea plurality of other transmitters are active and transmitting.
 15. Thesystem of claim 11, further comprising determining a power setting basedon a power measurements of at least one previously received packet. 16.The system of claim 11, wherein the error vector probe packet istransmitted while a second transmitter is active and transmitting ananalog zero signal.
 17. The system of claim 11, wherein the analog zerosignal comprises an orthogonal frequency-division multiplexing symbolfor a voltage input that is substantially zero.
 18. A method of probinga wired communication channel comprising: a) transmitting a first errorvector probe packet from a first transmitter, while a plurality oftransmitters in a system are active and transmitting on the wiredcommunication channel; b) receiving the first error vector probe packetat a network controller; c) determining, at the network controller, theerror vector magnitude for the first transmitter based on the firstreceived error vector probe packet; and d) estimating, at the networkcontroller, channel characteristics based on the received first errorvector magnitude.
 19. The method of claim 18, further comprisingrepeating the steps for each of the plurality of transmitters.
 20. Themethod of claim 18, further comprising estimating a signal-to-noiseratio and a data capacity based on the error vector magnitude.
 21. Awired communication device comprising: a) a receiver configured toreceive a control packet that indicates when a plurality of transmittersare active and transmitting on a wired communication channel; and b) atransmitter configured to transmit the error vector probe packet whenindicated by the control packet that the plurality of transmitters areactive and transmitting on a wired communication channel.
 22. A wiredcommunication device comprising: a) a receiver configured to receive anerror vector probe packet transmitted on a wired communication channelwhen a plurality of devices in a system are active and transmitting onthe wired communication channel; and b) a processor configured tomeasure an error vector magnitude for the first transmitter based on thereceived error vector probe packet and to estimate a channelcharacteristic based on the error vector magnitude.
 23. A tangiblecomputer readable storage medium upon which instructions are stored forperforming the following: a) receiving a first error vector probe packetthat was transmitted by a first transmitter while a second transmitterin a system is transmitting on the wired communication channel; b)measuring an error vector magnitude for the first transmitter based onthe received first error vector probe packet; and c) estimating channelcharacteristics based on the error vector magnitude.